A semiconductor device including: a transistor in which a source terminal is connected to a voltage supply line of a power supply voltage or a reference voltage; and a substrate bias variable resistance element connected between a semiconductor region where a channel of the transistor is formed and the voltage supply line, is known (for example, refer to Patent Document 1). A substrate bias decision part decides a magnitude relation held by an electric potential of the semiconductor region relative to a source potential by a variable resistance value of the substrate bias variable resistance element.
Besides, a semiconductor integrated circuit device operating based on a control signal, and including a substrate potential generation circuit making a substrate bias deep by pumping an electric charge from a semiconductor substrate at an operation time, and whose output becomes high impedance at a non-operation time, is known (for example, refer to Patent Document 2). A switch circuit operates based on the control signal, becomes a conduction state at the non-operation time of the substrate potential generation circuit to make the electric potential of the semiconductor substrate a power supply voltage, and becomes a non-conduction state at the operation time of the substrate potential generation circuit.
Besides, an A/D converter including a current mirror circuit in which an input analog current is applied on an input terminal, and plural reference current sources respectively connected to plural output terminals of the current mirror circuit is known (for example, refer to Patent Document 3).
[Patent Document 1] Japanese Laid-open Patent Publication No. 2010-80807
[Patent Document 2] Japanese Laid-open Patent Publication No. H9-326688
[Patent Document 3] Japanese Laid-open Patent Publication No. H3-216023
Patent Document 1 discloses an art to apply a substrate bias at low cost without having an additional power supply for the substrate bias generation at inside or outside.
Here, there is a case when the substrate bias, the power supply voltage, or the reference voltage varies caused by the operation of the transistor and so on. In this case, there is a case when a leak current of the transistor increases, and a power consumption increases.